Wednesday, May 12, 2010

7×57 Mauser

It shouldn’t be surprising how many modern hunting cartridges can trace their ancestry back to military based roots. Ammunition designed for and used in the military gained popularity with service members returning from war who favored cartridges they were familiar with for hunting medium and large game. The 7×57mm Mauser, or .275 Rigby as it is known in the United Kingdom, is one such cartridge.

Initially designed by German manufacturer Mauser in 1892 it quickly earned a reputation as a solid performing round. The Spanish quickly adopted the model 1893 7mm Mauser and used it to great effect against US troops at the battle of San Juan Hill in Cuba during the Spanish-American War. US Military leaders painfully learned the effectiveness of the Mauser and the 7mm cartridge it was chambered for. So impressed were they that they based the 1903 Springfield rifle and the .30-06 cartridge off of the Mauser design. In fact, so many design aspects of the Model 93 Mauser were used in the Springfield that the United States was forced to pay royalties to Mauser for a number of years.

The United States wasn’t the only nation to take note of the abilities of 7×57mm ammunition. British firearm manufacturer John Rigby & Company adopted the Mauser cartridge after acquiring a number of Mauser actions and renamed it the .275 Rigby. For decades they built hunting rifles based on the now world famous Mauser design. It was under this name that the 7mm Mauser became famous in Africa as an elephant hunting round. Though significantly underpowered as a dangerous game load, Scottish hunter Walter Bell became famous for killing over 1,000 elephants with rifles chambered for the cartridge. His success however was more attributable to his shot placement rather than the inherent ability of the .275 Rigby. Bell focused on using head-shots to quickly drop massive pachyderms, even going so far as to saw the skull of one of the elephants in two so that he could better know the exact location and size of the brain. Due to the size and toughness of the elephant skull, Bell only used 173 grain full metal jacketed bullets in order to get adequate penetration.

Despite Bell’s success harvesting elephants, the 7mm is really at home as a medium game cartridge suitable for hunting deer, and elk. With performance approximating that of the .270 Winchester, larger game such as bear and even moose can be successfully harvested with accurate shot placement. Modern 7×57mm loads are most often found topped with light weight 139-145 grain bullets, making the 7×57mm is a fairly flat shooting high velocity cartridge.

Modern factory loads are by and large fairly conservative with the pressures generated: after all, the 7mm Mauser got its start as a blackpowder cartridge. To truly get the maximum out of the round it helps to hand load your own for use in modern rifles. Propelled by 50.0 grains of medium-burning H414 powder a 7mm 139 grain bullet is capable achieving speeds approaching 3,000 feet per second at the muzzle, giving it a muzzle energy of around 2,300 foot-pounds. The problem with loading rounds over the 57,000 psi that the round is rated for is that few modern rifles are chambered for the round (one notable exception being the single-shot Ruger No. 1A), and many of the older 7mm Mausers that were imported into the American market are made from older steel that is not capable of handling higher pressures. As always, when developing a load for your 7×57mm rifle start at 50% of the recommended load found in your reloading manual and slowly work up to the desired load, keeping an eye on spent casings for signs of overpressure.